Experimental round-robin differential phase-shift quantum key distribution
Yu-Huai Li, Yuan Wen Cao, Hui Dai, Jin Lin, Zhen Zhang, Wei Ren Chen, Yu Xu, Jian-Yu Guan, Sheng‐Kai Liao, Juan Yin, Qiang Zhang, Xiongfeng Ma, Cheng-Zhi Peng, Jian-Wei Pan · Physical Review A · 2016
In conventional quantum key distribution (QKD) protocols, security is guaranteed by estimating the amount of leaked information. Such estimation tends to overrate, leading to a fundamental threshold of the bit error rate, which becomes a bottleneck of practical QKD development. This bottleneck is broken through by the recent work of round-robin differential phase-shift (RRDPS) protocol, which eliminates the fundamental threshold of the bit error rate. The key challenge for the implementation of the RRDPS scheme lies in the realization of a variable-delay Mach--Zehnder interferometer, which requires active and random choice of many delays. By designing an optical system with multiple switches and employing an active phase stabilization technology, we successfully construct a variable-delay interferometer with 127 actively selectable delays. With this measurement, we experimentally demonstrate the RRDPS protocol and obtain a final key rate of 15.54 bps with a total loss of 18 dB and an error rate of 8.9%.